超级居群：连接生境多样性和生物多样性之桥

在达尔文（1859）看来,新物种只有通过竞争或者自然选择的方式淘汰原有物种才能进入由其他物种占据的生境并成功定居下来。然而,新物种进入生境并成功定居还有另外一个途径,那就是由于超级居群能在全球尺度上改变整个地球环境,从而能在原有环境中创造出一些全新的微环境来,正是这些全新的微环境使新物种避开了和原有定居者的剧烈竞争,很容易地进入了一直由其他物种占据的生境中并成功地定居下来。换句话说,超级居群导致了全球环境的分化,导致了全球尺度上的生境多样性。同时,超级居群通过环境的异质化为新物种准备好了很多全新的微环境,新物种在全新的微环境中的成功定居实现了新物种和原有定居者的长期共存。而这种长期共存导致了整个生物圈的生物多样性的增加。超级居群是地球上很多新环境的创造者,是生境多样性和生物多样性之间的桥梁,据此就能很容易地解释新物种为什么不时能和原有定居者共存甚至依赖于原有定居者,从而导致二者间剧烈竞争缺失的现象。     

Foraging behaviour and habitat use by Antechinus flavipes and Sminthopsis murina (Marsupialia: Dasyuridae) in response to predation risk in eucalypt woodland

We examined the foraging behaviour and habitat use of two species of small Australian mammal (Antechinus flavipes and Sminthopsis murina) in response to predation risk in remnant eucalypt woodland. Predation risk was manipulated by providing refuge in the form of ground level wire netting to reduce risks from avian and mammalian predators. Giving-up-densities (GUD) using artificial food trays (20 mealworms in 1.5 l vermiculite) quantified the foraging behaviour in response to predation risk, by measuring the quitting harvest rate. Both A. flavipes and S. murina had lower GUDs (number of mealworms remaining) under the netting than in the open, most likely because these areas have lower predation risk. Animals also made greater visits to tracking tunnels under the netting compared to in the open. Tracking animal movements using fluorescent pigments also revealed preference for natural microhabitats that were structurally complex with animals moving most where logs and rock crevices were present. These results suggest that small mammals may use habitat structure to reduce their risks of predation. If future studies are able to demonstrate commensurate population-level responses, manipulation of habitat may be a useful management option to complement the direct control of exotic predators such as foxes and feral cats.     

凉水国家级自然保护区狍冬季对微生境的选择

2008年11—12月份,在凉水国家级自然保护区采用样线法对狍的冬季微生境选择做了研究。一共测定了76个利用样方以及81个对照样方的20种生态因子。结果表明,凉水自然保护区狍冬季偏好选择位于针阔混交林、最近乔木距离3m、最近乔木高度在10m之内、最近乔木郁闭度60%、最近灌木距离0.5m、最近灌木基径在0.4～1.0cm,针叶树百分比在1%～25%,乔木密度0.14株/m2,灌木密度0.10丛/m2,1m以下植被覆盖度1%,2.5m以下植被覆盖度4%,坡度1°～3°、雪深17cm,海拔340～370m,人为干扰距离1000m的生境。主成分分析显示前7个主成分的特征值都大于1,且累积的贡献率达到87.522%,说明这7个成分基本上包括了狍微生境的信息,其中最近乔木胸径、最近灌木基径、1m以下植被覆盖度对第一主成分的贡献较大;最近乔木胸径、坡度对第二主成分的贡献较大;最近灌木高度、针叶树百分比对第三主成分的贡献较大。     

Tree identity surpasses tree diversity in affecting the community structure of oribatid mites (Oribatida) of deciduous temperate forests

The role of tree diversity and identity as determinants of soil animal community structure is little understood. In a mature deciduous forest dominated by beech we identified clusters of one, two and three tree species of beech, ash and lime allowing to investigate the role of tree species diversity and identity on the density and community structure of oribatid mites. To relate oribatid mite community structure to environmental factors we measured leaf litter input, fine root biomass, mass of organic layers, topsoil pH and C and N content. We expected oribatid mite density to increase with increasing tree diversity, but we expected the effects of tree species identity to override effects of tree diversity. Further, we hypothesized the density of oribatid mites to be reduced by the presence of beech but increased by the presence of lime and ash. As expected tree diversity little affected oribatid mite communities, whereas tree species identity strongly altered density and community structure of oribatid mites. However, in contrast to our expectations the density of oribatid mites was highest in presence of beech indicating that many oribatid mite species benefit from the presence of recalcitrant litter forming thick organic layers. Especially Oppioidea benefited from the presence of beech presumably due to an increased availability of food resources such as fungi and nematodes. Lower density of oribatid mites in monospecific clusters of lime and ash suggests that oribatid mites did not benefit from high quality litter of these species. Notably, large and strongly sclerotized oribatid mite species, such as Steganacarus magnus and Chamobates voigtsi, benefited from the presence of ash and lime. Presumably, these large species better resist harsh microclimatic conditions in shallow organic layers.     

超级居群:连接生境多样性和生物多样性之桥(英文)

在达尔文(1859)看来,新物种只有通过竞争或者自然选择的方式淘汰原有物种才能进入由其他物种占据的生境并成功定居下来。然而,新物种进入生境并成功定居还有另外一个途径,那就是由于超级居群能在全球尺度上改变整个地球环境,从而能在原有环境中创造出一些全新的微环境来,正是这些全新的微环境使新物种避开了和原有定居者的剧烈竞争,很容易地进入了一直由其他物种占据的生境中并成功地定居下来。换句话说,超级居群导致了全球环境的分化,导致了全球尺度上的生境多样性。同时,超级居群通过环境的异质化为新物种准备好了很多全新的微环境,新物种在全新的微环境中的成功定居实现了新物种和原有定居者的长期共存。而这种长期共存导致了整个生物圈的生物多样性的增加。超级居群是地球上很多新环境的创造者,是生境多样性和生物多样性之间的桥梁,据此就能很容易地解释新物种为什么不时能和原有定居者共存甚至依赖于原有定居者,从而导致二者间剧烈竞争缺失的现象。     

Determination of a common forest life cycle assessment method for biodiversity evaluation

Forest biodiversity is highly linked with the occurrence of certain forest development phases (fdp) within the forest life cycle. Generally, the disintegration phase provides the highest biodiversity. The objective of the study was to test different existing forest life cycle assessment approaches aiming at developing a common reliable fdp assessment method. We tested and compared three approaches to record fdp in beech, mixed beech and spruce forests, in managed and unmanaged forests, and in four different plot sizes ranging from 125 to 2000 m². The main results of the fdp comparison are as follows:

(1)

In approximately two thirds of the cases the three considered methods did not yield a corresponding fdp record.

(2)

Generally, the larger the plot sizes, the larger the average fdp deviation in forest reserves.

(3)

The fdp deviation is stronger in beech or spruce dominated forest reserves than in mixed beech forest reserves.

(4)

Plots of 500 m² show most distinct numbers of microhabitats corresponding to the fdp sequence within the forest life cycle.

(5)

Furthermore, the managed forests mostly show lower fdp deviation than the forest reserves.

One approach resulted in the most differentiated portrayal of the studied forest structures compared to the other two as shown by the facts that, (a) the studied forests are seen to be divided up into more fdp than when applying the other two methods, and that (b) the dominant fdp changed depending on the forest community and plot size reflecting different growth conditions and probabilities to meet large dimensioned trees during records, respectively, and (c) considering the distribution of microhabitats which are crucial for xylobiontic (saproxylic) organisms, this approach resulted in the assumed biodiversity patterns with increasing microhabitat numbers up to the disintegration phase thus it was used as a basis for the creation of an optimized fdp assessment method as a tool for common and standardized use in forest ecology and biodiversity research.     

Arthropod assemblages in vegetative vs. humic portions of epiphyte mats in a neotropical cloud forest

Epiphyte mats (contiguous pieces of live and dead epiphytes perched upon branches of trees) are a conspicuous component of tropical cloud forests and harbor diverse meso- and microarthropod communities. We investigated differences in arthropod assemblage structure between the vegetative (green) and humic (brown) portions of epiphyte mats in a lower montane forest in Monteverde, Costa Rica. Because of qualitative differences between the two substrates, we hypothesized that they would support different arthropod communities and that variation in community parameters would be linked to the quantity of brown material present in a mat sample. The green fraction contained twice as many individuals and species per gram dry mass than the brown fraction. Morphospecies composition was very similar between green and brown portions, but the relative abundance of several taxa differed significantly between the substrates. Contrary to our prediction, total arthropod abundance and richness in a sample were not correlated with the proportion of brown material present. In laboratory trials, the most common morphospecies of oribatid mite in this system showed a preference for brown substrates.     

Herpetofauna diversity and microenvironment correlates across a pasture-edge-interior ecotone in tropical rainforest fragments in the Los Tuxtlas Biosphere Reserve of Veracruz, Mexico

We evaluated the relationship between amphibian and reptile diversity and microhabitat dynamics along pasture-edge-interior ecotones in a tropical rainforest in Veracruz, Mexico. To evaluate the main correlation patterns among microhabitat variables and species composition and richness, 14 ecotones were each divided into three habitats (pasture, forest edge and forest interior) with three transects per habitat, and sampled four times between June 2003 and May 2004 using equal day and night efforts. We measured 12 environmental variables describing the microclimate, vegetation structure, topography and distance to forest edge and streams.After sampling 126 transects (672 man-hours effort) we recorded 1256 amphibians belonging to 21 species (pasture: 12, edge: 14, and interior: 13 species), and 623 reptiles belonging to 33 species (pasture: 11, edge: 25, and interior: 22 species). There was a difference in species composition between pasture and both forest edge and interior habitats. A high correlation between distance to forest edge and temperature, understorey density, canopy cover, leaf litter cover, and leaf litter depth was found. There was also a strong relationship between the composition of amphibian and reptile ensembles and the measured environmental variables. The most important variables related to amphibian and reptile ensembles were canopy cover, understorey density, leaf litter cover and temperature.Based on amphibian and reptile affinity for the habitats along the ecotone, species were classified into five ensembles (generalist, pasture, forest, forest edge and forest interior species). We detected six species that could indicate good habitat quality of forest interior and their disappearance may be an indication of habitat degradation within a fragment, or that a fragment is not large enough to exclude edge effects. Different responses to spatial and environmental gradients and different degrees of tolerance to microclimatic changes indicated that each ensemble requires a different conservation strategy. We propose to maintain in the Los Tuxtlas Biosphere Reserve the forest remnants in the lowlands that have gentler slopes and a deep cover of leaf litter, a dense understorey, and high relative humidity and low temperature, to buffer the effects of edge related environmental changes and the invasion of species from the matrix.     

Carabid beetle (Coleoptera: Carabidae) diversity in the black spruce succession of eastern Canada

This study provides the first assessment of carabid beetle diversity in a natural forest context that encompasses a complete black spruce (Picea mariana) natural succession. Boreal forest conservation has been based on several assumptions about forest age that only consider species richness without accounting for species composition. It has also been guided by studies of incomplete chronologies that do not include naturally burned or old-growth stages. Twenty-one forest stands of different ages following fire - from recently burned to old-growth stages (0-340 years of age) - were sampled, revealing a strong relationship between age of forest and diversity of Carabidae. Over time, species richness followed a parabolic U-shaped pattern both with observed (Obs) and predicted richness (ACE). Chronological clustering identified four groups of species in the succession: the ‘burned’ group characterized 0-2-year-old forests, ‘regenerating’ (21-58 year), ‘mature’ (70-170 year) and ‘old-growth’ (177-340 year). The time spans corresponding to each of these assemblages lengthen with age of forest at an exponential rate. Ward’s and K-means (clustering without constraint) provided support for the four assemblages but showed variation between individual successions, particularly for the ‘regenerating’ assemblage, identified as the most heterogeneous. The IndVal method identified characteristic species in every stage of the succession, particularly Sericoda spp. in the burned stage and Dromius piceus and Platynus mannerheimii associated with old-growth stands. The results obtained here show that diversity of Carabidae varies in primeval conditions according to age of forest and such variation should be taken into account when conservation issues are involved.     

A test of the hierarchical model of habitat selection using eastern massasauga rattlesnakes (Sistrurus c. catenatus)

Understanding the process animals follow to select habitat, rather than just documenting the habitat they use, will improve our ability to predict how the animals use habitat in other locations and how they will respond to changes in habitat. Animals are usually assumed to select habitats hierarchically, preferentially using specific macrohabitats at a landscape scale and specific microhabitats within the preferred macrohabitats. We used four years of telemetry data from 34 individuals to test this hierarchical model of habitat selection with eastern massasauga rattlesnakes (Sistrurus c. catenatus) in Ontario. Snakes were selective at the microhabitat scale, preferentially using locations with closer retreat sites and shrubs than random. Gravid females were most selective, using sites with more rock cover and less canopy closure than sites used by males and nongravid females. Snakes preferred forested habitats for hibernation and steadily increased their use of open, wetland, and edge habitats to a peak in mid-summer. Landscape-scale habitat preferences were generally mild and could be explained by the relative availability of suitable microhabitat within habitats, suggesting habitat selection was primarily driven by microhabitat preferences. The lack of selectivity at the landscape scale may be a consequence of fine-grained differences between habitats that allow massasauga rattlesnakes to find suitable microhabitats in all available macrohabitats. For species that select habitat primarily at the microhabitat scale (e.g., the rattlesnakes we studied), landscape-scale modeling of habitat use will only be effective to the extent habitats reflect the availability of suitable microhabitat within.